Identification of ethanol-inducible promoters in rice

Abstract

Rice (Oryza sativa L.) has been distributed and cultivated throughout Thailand. Thai rice germplasm could be used as genetic resources for functional genomic analysis covering the system for controlling gene expression. The response to ethanol of normal plants indicated that the ethanol-inducible system may present in plants. Thus, effects of ethanol on the growth of rice plants were examined and ethanol-inducible genes in young rice panicles were identified. The Pathumthani 1(PTT1) cultivas was used in this study. The results showed that 1% ethanol showed non-toxic effects to the rice plants. Using cDNA-AFLP, thirty-four transcript-derived fragments (TDFs) from panicles showed differential responses to ethanol application. The obtained TDFs were corresponding to genes involving different pathways including stress response and transcriptional regulation. Using semi-quantitative RT-PCR, five TDFs, which homologous to Os07g0240300, Os02g0175700, Os05g0392100, Os03g0569000 and Os07g627300 and adh2, were up-regulated. Among them, Myb-related protein-like (Os07g627300) is highly conserved and generally expressed in several rice tissues, possibly be used to control a wide range of genes in different tissues. The 5’ upstream region (UTR) Os07g627300 was isolated and cis-acting regulatory elements were analyzed. The obtained 5’ UTR was a TATA-less promoter containing a number of motifs involved in stress responses. Furthermore, the biodiversity of Thai rice may also provide potent resources for the development of functional food, for example, cereal grass juices from rice. Therefore, juices squeezed from grasses harvested at the jointing stage for fourteen colored and white Thai rice cultivars and wheat (Triticum aestivum L.) were analyzed for antioxidant activity. Additionally, the total phenolic content (TPC) and total monomeric anthocyanin content (TMAC) were determined. Colored (purple) rice grass juices exhibited greater antioxidant potential than the grass juices from white rice and wheat. The colored rice cultivar ‘Kum Doisaket’ exhibited the highest antioxidant activity in all assays (p<0.05). Correlation analysis indicated that the TPC and TMAC were responsible for the antioxidant activity. The DNA protective properties of the colored rice cultivars ‘Kum Doisaket’ and ‘Kum Noi’ and wheat were examined. Only the ‘Kum Doisaket’ cultivar exhibited a dose-dependent DNA protective effect. The notable antioxidant efficacy for the ‘Kum Doisaket’ cultivar may be influenced by the high level of anthocyanins present in its grass juice. This finding provides an alternative way to regulate gene expression and suggests the possibility of developing functional foods from colored rice grass. Rice is a model plant of monocots; therefore, this knowledge could be widely applied to the other cereals.